1. Field of the Invention
The present invention is related to a method and for bending forging an artistic metallic pipes and especially to bending forging of a metallic pipe, wherein, a pressure resistive removable and bendable die core is provided in a pipe bore, and a flexible die set is provided for receiving the pipe body, in this way, when it is under action of a normal forging force, a straight metallic pipe having an artistic contour can be forged into a bended metallic pipe having an artistic contour and a smooth curvature.
2. Description of the Prior Art
In the well known metallic pipe processing techniques in the markets, a metallic article made by forging has much higher compression strength than that of the metallic articles made by casting or extruding techniques; therefore, when compressive strength of the metallic articles to be forged is critical, the metallic articles always are made by forging. In the manufacturing techniques used nowadays for making an artistic metallic pipe however, there have been swaging techniques to make a metallic embossed pipe with high compressive strength, the swaging techniques include using of a rotary swager, a stationary-spindle swager, a creeping-spindle swager, an alternate-blow swager or a die-closing swager etc., metallic pipes made by progressive swaging in such techniques have on both the inner and the external walls thereof embossed patterns, these pipes are generally called herein artistic metallic pipes; no matter the artistic metallic pipes formed have any of various embossment, such swaging techniques are all available only for processing normal metallic pipes. Artistic metallic pipes formed by swaging techniques are certainly all straight in shape; There is no such technique in the markets for making bended pipes with smooth curvature but without damage to the predetermined embossments on the inner and the external walls thereof, this has been a regret in the field of pipe forging, and the problems thereof are:
1. The pipe bores of the pipes to be forged into bended pipes can not be installed therein with and removed therefrom supporting die cores. PA1 2. Die sets for forging bended pipes are absent, which die sets are required to be deformable following bending moment and to distribute uniform action force. PA1 1. The die core in a pipe bore is made from a steel rope, the wall of the pipe bore has an artistic pattern thereon, according to strength requirement and thickness of the metallic pipe wall, suitable amount of small steel balls or iron sand are added into plastisol and stirred under the melting temperature (80-100.degree. C.) thereof in a conventional pounding mixer to form thoroughly a mixed filler; the filler is introduced into the pipe bore by a well known screw feeding mode to a saturated state, temperature during introducing of the filler is controlled between 85-45.degree. C.; the plastisol uniformly added with steel balls or iron sand in the pipe bore then gradually gets denser, after cooling, the die core filled with the steel rope renders the artistic metallic straight pipe to form a solid straight pipe. In this way, the steel cord and the plastisol in the die core which are flexible make the pipe suitable for bending forging; the steel balls or iron sand in the pipe bore enable the die core to be resistant to forging pressure on the pipe wall so that the pipe wall can be prevented from over deforming; the die core can be slightly warmed up after bending forging to melt the plastisol, so that the die core bended in pursuance of the action of bending moment can be taken out of the pipe bore easily. PA1 2. The die set used is made of spring steel and includes an upper and a lower die housing mating with each other, the die housings have on the two ends thereof supporting axles and formed therein two troughs which are provided respectively on the top and the bottom thereof with suitable amount of hard bracing stubs, both the lateral walls or die limiting sheet plates are provided with a plurality of "V" shaped gaps capable of absorbing bending deformation quantity, the external top and bottom surfaces respectively of the upper and lower die housings are provided thereon with two laminated springs; thus the solid straight pipe is placed between the two lateral walls or die limiting sheet plates of the troughs, the remaining space in the troughs are filled with liquid polyurethane (namely PU glue) to a saturated state, then the liquid polyurethane is heated to solidify under its solidifying temperature, it can thus envelop the solid straight pipe in the troughs and buries the hard bracing stubs, this therefore forms a specified die set used to forge the solid straight pipe to form a bended pipe. The "V" shaped gaps on the lateral walls of the die housings used for absorbing bending deformation quantity hold the solidified polyurethane to thereby maintain a stable deformation rate in forging to obtain the required bending curvature; the two laminated springs can distribute the forge action force uniformly to the whole die set, so that every part of the solid straight pipe in the die set bears equalized forge action force, and the die set can be bent to a desired curvature. PA1 3. The hard bracing stubs of suitable amount on the upper and lower die housings and buried in the polyurethane are used for bracing the areas near the artistic metallic straight pipe where larger bracing force is required; so that the areas on the pipe wall where bending curvature is too large or dead corners are formed can get sufficient bearing force to resist bending moment. PA1 4. By the nature of instant melting under a low temperature of the plastisol in the die core, the bended pipe forged can have its pipe wall released from the plastisol easily by slight warming and allows the die core to be taken out to reveal the non-damaged and perfect bended pipe.